Norbornenyl phenolic compounds

ABSTRACT

Novel norbornenyl phenolics useful as antioxidants are defined by the following structural formula: ##STR1## where R 1 , R 2 , and R 3  are individually selected from hydrogen and alkyl groups of 1 to 3 carbon atoms; R 4  is selected from hydrogen, alkyl groups containing 1 to 12 carbon atoms, and substituted and unsubstituted alicyclic groups of 4 to 8 carbon atoms; R 5  is selected from alkyl groups containing 1 to 6 carbon atoms, and substituted and unsubstituted alicyclic groups of 4 to 8 carbon atoms; R 7  is selected from alkylene and alkenylene groups containing 1 to 8 carbon atoms; and R 8  is selected from hydrogen, alkyl and alkenyl groups containing 1 to 8 carbon atoms.

BACKGROUND OF THE INVENTION

Cyclopentadiene is present to the extent of about 15% in the naphthacracker C₅ by-products stream from ethylene plants. One way to disposeof the C₅ by-products stream is to use it as a fuel stock; a better useis as a source of petrochemicals. The most sought-after component of theC₅ by-products stream is isoprene, which is also present at about 15%level. With the soaring price of natural rubber, pressure is mounting toexpand synthetic polyisoprene production. For every pound of extractisoprene capacity that comes on stream, there will be a pound ofcyclopentadiene. Thus, it stands to reason that with the sharp rise inthe cost of crude oil, ethylene producers will have a strong incentiveto find the most profitable uses for the by-products. In this context,cyclopentadiene is high on the list since its removal from the C₅ streamis easily accomplished at the first step of the C₅ purification process.

It is, therefore, desirable to promote reactions involvingcyclopentadiene and derivatives thereof to produce useful products.

SUMMARY OF THE INVENTION

This invention relates to novel norbornenyl phenolics which are preparedby reacting substituted or unsubstituted cyclopentadiene with phenoliccompounds at elevated temperature to produce reaction products whichhave antioxidant activity.

DETAILED DESCRIPTION OF THE INVENTION

Cyclopentadienes that can be reacted with phenolic compounds have thefollowing structure: ##STR2## where R¹, R² and R³ are independentlyselected from hydrogen and alkyl radicals of 1 to 3 carbon atoms,preferably, R¹, R² and R³ are individually selected from hydrogen andmethyl groups.

Suitable phenolic compounds that can be reacted with cyclopentadieneinclude those represented by the following structural formula: ##STR3##where R⁴ is hydrogen, an alkyl group of 1 to 12 carbon atoms, or asubstituted or unsubstituted alicyclic group of 4 to 8 carbon atoms,preferably R⁴ is an alkyl group of 1 to 6 carbon atoms positioned at theopen ortho position; R⁵ is an alkyl group of 1 to 12 carbon atoms or asubstituted or unsubstituted alicyclic group of 4 to 8 carbon atoms,preferably R⁵ is an alkyl group of 1 to 6 carbon atoms; and R⁶ is analkenyl group of 2 to 12 carbon atoms, preferably 3 to 6, containing oneunsaturated bond, preferably positioned terminally. These phenoliccompounds are prepared by reacting an alkylene halide with a substitutedphenol in order to introduce the unsaturated group onto the phenyl ring.In a subsequent reaction with cyclopentadiene, the unsaturated groupmakes possible the formation of the norbornenyl phenolic. The reactionbetween an alkylene halide and a substituted phenol is carried out undera blanket of nitrogen in the presence of a solvent, such as dimethylformamide or dimethyl sulfoxide, and an alkali metal alkoxide catalyst,such as sodium methoxide.

Specific examples of alkylene halides include allyl halide such as allylbromide; allyl chloride; 6-chloro-1-hexene; 4-bromo-1-octene, andothers, all of which can contain lower alkyl substituents on the carbonchains. Suitable examples of substituted phenols which can be used inthe reaction with alkylene halides to produce phenolic compounds include2,6-di-t-butylphenol, 2-t-butyl-5 methylphenol, 2-octyl-6-t-butylphenol,2-t-butyl-6-cyclohexylphenol, 2-hexyl-6-cyclohexylphenol, and2-t-pentyl-6-methylcyclohexylphenols.

The reaction between a phenolic compound and cyclopentadiene isexemplified below by means of the following equation: ##STR4## where R¹,R², R³, R⁴, R⁵, and R⁶ are as previously defined; R⁷ is selected fromalkylene and alkenylene groups containing 1 to 8, preferably 1 to 4carbon atoms; and R⁸ is selected from hydrogen, and alkyl and alkenylgroups of 1 to 8, preferably alkyl groups of 1 to 4 carbon atoms.

The norbornenyl phenolics of this invention provide antioxidant functionin various materials, such as synthetic natural rubber,styrene-acrylonitrile rubber and other thermoplastics and elastomers.These novel compounds can be bound into a polymer backbone by variouspolymerization techniques and thus provide a number of significantadvantages which are characterized by the fact that such antioxidantsare not lost as a result of leaching or volatilization and they are notredistributed, which means that blooming is eliminated.

This invention will now be illustrated by a number of specific exampleswhich are presented for the purpose of elucidating the disclosure of theinvention claimed herein. These examples are not to be construed aslimiting in any way the scope of the appended claims.

EXAMPLE 1

This example illustrates preparation of a phenolic compound which issubsequently reacted with cyclopentadiene to form a novel norbornenylphenolic. The reactants are di-t-butylphenol and allyl bromide and theproduct is 4-allyl-2,6-di-t-butylphenol.

The reaction was carried out by charging a one liter, 3-necked reactorwith 11.8 g (0.218 mole) sodium methoxide and 200 ml of dry dimethylformamide. The suspension was stirred at room temperature. A solution of41.2 g (0.200 mole) of the substituted phenol in 100 ml of dry dimethylformamide was then added to the reactor and the contents thereof werestirred for one hour. Subsequently, 25 g (0.21 mole) of allyl bromidewas added over a period of 15 minutes with vigorous agitation, allowingthe reaction to exotherm freely. The exotherm reached 41° C. duringaddition of allyl bromide but dropped soon after all of the allylbromide was added. A sample was analyzed by vapor phase chromatographywhich showed 62% product formation. Then the reactor was heated and heldat 50° C. for one hour and then was allowed to cool down and remainovernight at room temperature. In the morning, water was added to thereactor with stirring, followed by toluene to extract the organicmatter. The toluene layer was washed with water 3 times in a largeseparatory funnel and then dried over sodium sulfate. The liquid wasfiltered off with suction and then evaporated to yield a reddish oilwhich was distilled under high vacuum.

EXAMPLE 2

Here, preparation of the norbornenyl phenolic is illustrated by thereaction of 4-allyl-2,6-di-t-butylphenol with cyclopentadiene, asdepicted by the following equation: ##STR5##

The reaction was undertaken by mixing 107 g (0.32 mole) of4-allyl-2,6-di-t-butylphenol with 85 g (0.64 mole) of dicyclopentadieneand charging the mixture to a stainless steel high pressure reactor.Reaction temperature was maintained at about 240° C. for about 4 hourswith pressure developing to about 50 psig. Under these conditions,dicyclopentadiene undergoes a retro Diels-Alder reaction to formcyclopentadiene. Samples were continuously taken for analysis. Afterabout 4 hours of reaction time, contents of the reactor were transferredto a flask and distilled under vacuum. The product distilled at 148° to152° C. at 1.5 mm of vacuum and was of pale yellow color. The productwas identified by NMR spectroscopy. NMR (CDCl₃) δ:1.43 (S, 18H, C--CH₃),1.61-2.94 (M, 9H, C--H), 3.25 & 3.36 (D, 2H, Ar--CH₂), 4.99 (S, 1H,O--H), 6.96 (S, 2 H, Ar--H).

EXAMPLE 3

This example demonstrates stabilizing or antioxidant properties of thenorbornenyl phenolic antioxidant of Example 2 compared to butylatedhydroxytoluene (BHT) antioxidant, 4-allyl-2,6-di-t-butylphenol ofExample 1, and a control sample without any antioxidant additive. Ineach instance, 0.68 g of a given antioxidant was mixed with 68 g ofreprecipitated synthetic natural rubber, i.e., polyisoprene, in aBrabender Plasticorder for two minutes at 80° C. No antioxidant wasadded to the control sample, it consisted only of SN rubber. Each samplewas prepared and tested for Mooney viscosity before and after agingpursuant to ASTM D-1646-72 test using a large rotor and 1-minute warm-uptime. Mooney buttons were aged at 70° for 10 days in an oven, asprescribed by ASTM D-573-67 test. Table I, below, symmarizes results ofthese tests.

                                      TABLE I                                     __________________________________________________________________________             Mooney         Mooney Viscosity                                                                              % Retained                                     Viscosity After No Aging                                                                     After 10 Days at 70° C.                                                               Viscosity                                            4-Min.                                                                             10-Min.   4-Min.                                                                             10-Min.                                                                            on                                              Im-  Shearing                                                                           Shearing                                                                           Im-  Shearing                                                                           Shearing                                                                           10-Min.                                Antioxidant                                                                            mediate                                                                            Time Time mediate                                                                            Time Time Values                                 __________________________________________________________________________    BHT      76   59   56   60   47   45   80                                     Norbornenyl                                                                   Phenolic of                                                                   Example 2                                                                              80   59   54   58   44   40   74                                     Allyl Compound                                                                of Example 1                                                                           76   58   55   49   37   34   62                                     None     76   55   54   <10  <10  <10  <20                                    __________________________________________________________________________

Results in the above table indicate viscosity retention of 74% for thenorbornenyl phenolic antioxidant versus 80% for BHT, a commonly usedantioxidant for synthetic rubbers and plastics. This reflects thatnorbornenyl phenolic antioxidant retains the physical properties afteraging nearly as well as BHT. The norbornenyl phenolic antioxidantperforms as well or better than other commercial antioxidants in termsof maintaining physical properties of polymers on aging. In service, BHTis known to suffer from the severe disadvantage of volatilization andextraction from the polymers. On the other hand, norbornenyl phenolicantioxidants, which contain a uniquely reactive double bond in thenorbornenyl moiety, can be polymerized into the backbone of the polymerand thus become immune to volatization and extraction losses.

I claim:
 1. Novel compounds defined by the following structural formula:##STR6## where R¹, R², and R³ are individually selected from hydrogenand alkyl groups of 1 to 3 carbon atoms; R⁴ is selected from hydrogen,alkyl groups containing 1 to 12 carbon atoms, and substituted andunsubstituted alicyclic groups of 4 to 8 carbon atoms; R⁵ is selectedfrom alkyl groups containing 1 to 6 carbon atoms, and substituted andunsubstituted alicyclic groups of 4 to 8 carbon atoms; R⁷ is selectedfrom alkylene and alkenylene groups containing 1 to 8 carbon atoms; andR⁸ is selected from hydrogen and alkyl and alkenyl groups containing 1to 8 carbon atoms.
 2. Compounds of claim 1 wherein R¹, R², and R³ areindividually selected from hydrogen; R⁴ and R⁵ are individually selectedfrom alkyl groups of 1 to 6 carbon atoms; R⁷ is selected from alkylenegroups containing 1 to 4 carbon atoms; and R⁸ is selected from alkylgroups containing 1 to 4 carbon atoms.
 3. Compounds of claims 2 whereinR⁴ and R⁵ are selected from t-alkyl groups of 4 to 6 carbon atoms. 4.Compounds of claim 2 wherein R¹, R², and R³ are hydrogens, both R⁴ andR⁵ are t-butyl groups, R⁷ is a methylene group, and R⁸ is hydrogen. 5.Compounds of claim 4 wherein R⁴ group is located on the open orthoposition relative to the hydroxyl group.